1. Field of the Invention
The present invention relates to electric machines and, more particularly, to a DC stepping motor incorporating a printed circuit rotor.
2. Description of the Background
Simplicity and standardization are the basic prerequisites for tooling and machinery designed for mass production of industrial products. This is especially true of automatic processing systems where the operative component parts must have the flexibility to carry out different processing procedures using different work-pieces.
For example, a properly designed automatic processing system can complete a variety of operations such as lathe cutting, drilling, planning, milling, abrading, and boring. Moreover, the system should be capable of multiple sequential operations and/or multiple concurrent or combined operations.
Computer or processor-controlled systems provide the necessary flexibility. However, a precision electro-mechanical interface is required in such systems to convert software commands into mechanical movement. Typically, precision electric motors are used for this purpose.
For example, U.S. Pat. No. Re. 25,305 reissued Dec. 25, 1962, shows a commutating motor with an axial (or disk-type) structure which helps in reducing the size of the motor. The motor has a disk-type rotor with a number of coiled windings located radially about the disk. As shown in FIG. 3, the coiled armature windings 11 are alternately positioned on both sides of the disk 13, and all the windings 11 are connected in series via commutating segments 7 and 12. A stator is provided which includes two pairs of bi-polar magnets 17 and 18. Each pair of bi-polar stator magnets 17 and 18 flanks the disk rotor 13 and conforms to the armature windings thereon, and the two pairs are located 180.degree. apart. As the disk rotor 13 rotates, brushes 19 and 20 contact the commutating segments 7 and 12 thereby directing a DC voltage to the proper armature windings. The resulting continuous drive characteristics resemble those of a conventional DC motor, i.e., the speed is highly dependant on the DC input voltage and the load.
U.S. Pat. No. 3,737,697 issued to Kitamor et al. shows another example of a disk-type commutating motor. In this case, a printed circuit rotor is disclosed to further reduce the size of the motor.
Although the disk-type commutating motors as described above provide compact and powerful electro-mechanical conversion, they are continuous drive motors and are incapable of instantaneous starting and stopping. Hence, disk-type commutating motors are often incapable of the precise intermittent control needed computer or processor-controlled manufacturing systems.
Stepping motors were developed to overcome the above-described problems. Stepping motors may be controlled to execute and maintain a fixed angular displacement. This is usually accomplished by pulsed control signals from a central processor. However, unlike commutating motors, stepping motors are reluctance machines in which a permanent magnet rotor typically strives to align itself with an electrically-excited stator to minimize reluctance. Stepping motors (like commutating motors) may be constructed in an axial form, but this requires a permanent magnet stator and electrically-excited rotor. This in turn requires some means to convey the pulsed DC control signals to the rotor windings during rotation, and it requires a fixed arrangement of rotor windings and stator magnets to insure precise and continued incremental rotation with each additional control pulse.
It would be greatly advantageous to employ a disk-type rotor as in the Haydon Re. '305 patent in a stepping motor for machine tool applications as shown and described in the parent U.S. patent application Ser. No. 258,088 filed Oct. 17, 188 (which is, in turn, a continuation of Ser. No. 426,188 filed Sep. 28, 1982).
The Applicant is aware of European Patent Application 86107389.0 (Publication No. 0208213). This application claimed a priority based on U.S. Ser. No. 426,188 (the parent of the present application). A copy of this reference is provided herewith.